The present invention relates to an automatic lighting system for an automobile.
There is known an automatic lighting system which automatically closes a circuit interconnecting an electric power source and lamps, such as headlamps, to supply electric current to the lamps by bypassing a manual lighting switch. The service manual entitled "NISSAN LAUREL SERVICE MANUAL" published by Nissan Motor Company in November 1984 describes an automatic lighting system on page EL-65. Referring to FIG. 1, this known system is specifically described. There are shown in FIG. 1 a DC power source 10, i.e., a vehicle battery, a manual lighting switch 12, a left and a right headlamps 14a and 14b, and a clearance lamp 16. The manual lighting switch 12 is connected between the electric power source 10 and the lamps 14a, 14b and 16 such that input terminals X, Y, and Z thereof are connected to the power source 10 via fuses (no numerals), respectively, while output terminals X1, X2 are connected to the left headlamp 14a at its low beam terminal D and its high beam terminal H, output terminals Y1, Y2 are connected to the right headlamp 14b at its low beam terminal D and its high beam terminal H, and an output terminal Z1 is connected to the clearance lamp 16 via a noramlly closed contact of a relay 8d. The lighting switch 12 is manually operable to assume a plurality of positions including "OFF" position and "ON" position. The position of the lighting switch 12 controls the connection of the input terminal X to the output terminals X1 and X2, the connection of the input terminal Y to the output terminals Y1 and Y2, and the connection of the input terminal Z to the output terminal Z1 are controlled.
In order to supply electric current to the lamps 14a, 14b, and 16 by bypassing the manual lighting switch 12, there is provided a bypass circuit including relays 8b and 8d. The relay 8b has two pairs of normally open relay contacts, which pairs are connected between the low beam terminals of the headlamps 14a and 14b and input terminals X and Y, thereby bypassing the manual lighting switch 12. The relay 8d has a pair of normally open contacts connected between the clearance lamp 16 and the input terminal Z, thereby bypassing the manual lighting switch 12. The relays 8b and 8d have relay coils connected to be selectively responsive to current from power source 10. One end of the coil of the relay 8b is normally grounded through normally closed contacts of a relay 8c. The coil of the relay 8c is energized when the output terminal Z1 is disconnected from the input terminal Z while the manual switch 12 is in the "OFF" position. When the manual switch 12 assumes the other positions, the input and output terminals Z and Z1 are interconnected to supply electric current to the coil of the relay 8c, thus energizing same. This causes the normally closed contacts of the relay 8c to be caused.
The bypass circuit including the relays 8b and 8d is closed and permits electric current to be supplied from the power source 10 to the lamps 14a, 14b, and 16, to bypass the manual lighting switch 12 when an ignition switch 18, serving as an ignition indicator in this system, is turned on (closed), a charge indicator 24 is activated, and an oil pressure indicator 28 is activated. Thus, the lamps 14a, 14b, and 16 automatically turn on when the indicators 18, 24, and 28, which are indicative of the state of the engine, have predetermined states, respectively.
Describing these indicators, the ignition switch 18 is connected to both coils of the relays 8b and 8d via normally closed contacts of a relay 8a. The charge indicator 24 has one end connected to the power source 10 via fuse 20 and ignition switch 18 and an opposite end connected to a so-called L terminal of a voltage regulator 22 of an engine driven alternator, hereinafter called an alternator. The L terminal connects with the opposite end of the charge indicator 24. The oil pressure indicator 28 has one end connected to the power source 10 via the fuse 20 and ignition switch 18, and an opposite end connected to an oil pressure sensor switch 26.
One end of a coil of the relay 8a is connected to the power source 10 via the fuse 20 and ignition switch 18, and an opposite end connected to the L terminal via a diode D11 and to the oil pressure sensor 26 via a diode D12.
The voltage at the L terminal rises from a low level to a high level after the alternator 22 has produced an output high enough to cause energization of a stator coil, i.e., when the engine operation has been stabilized after completion of start-up operation. The charge indicator 24 turns on when the voltage at the L terminal assumes the low level, and turns off when the voltage at the L terminal rises to the high level.
The oil pressure rises to open the oil presure sensor 26 after the engine operation has become stable. Thus, the oil pressure indicator 28 turns on when the oil pressure sensor 26 is closed and turns off when the oil pressure sensor 26 is opened.
Since, as mentioned before, the opposite end of the coil of the relay 8a is connected to the L terminal and the oil pressure sensor 26, the electric current is supplied to the coil of the relay 8a when the voltage at the L terminal assumes the low level and/or the voltage appearing at the oil pressure sensor 26 assumes the low level, thus energizing the relay 8a to open its normally closed contacts. In other words, the relay 8a is energized if the engine fails to operate in a stable manner after a start-up operation initiated by closing of the ignition switch 18.
When the engine operation becomes stable, the voltage at the L terminal assumes the high level and the oil pressure sensor 26 opens. Under this condition, no current passes through the coil of the relay 8a, thus leaving the normally closed contacts thereof closed. Thus, the electric current is supplied from the power source 10 to the coils of the relays 8b and 8d via the ignition switch 18, fuse 20, and normally closed contacts of the relay 8a. This energizes of the coils of the relays 8b and 8d. Energization of the coil of the relay 8b closes its normally open contacts, while the energization of the coil of the relay 8d closes its normally open contacts, so electric current from the power source 10 flows to the low beam terminals D of the headlamps 14a and 14b and to the clearance lamp 16. As a result, the headlamps 14a, 14b and clearance lamp 16 turn on automatically when the engine operation becomes stable in response to the manual lighting switch 12 being placed in the "OFF" position.
In the above mentioned state, where the headlamps 14a, 14b, and clearance lamp 16 turn on when the manual lighting switch 12 is turned off so the system to operates in an automatic lighting mode, if the voltage at the L terminal drops to the low level or the oil pressure sensor 26 turns on, the coil of the relay 8a is energized, causing the normally closed contacts thereof to open. This cuts off the supply of electric current to the coils of the relays 8b and 8d. As a result, the headlamps 14a, 14b, and clearance lamp 16 turn off.
If, in the above-mentioned state, the ignition switch 18 is turned off, the supply of electric current to the coils of the relays 8b and 8d is cut off, causing the headlamps 14a, 14b, and clearance lamp 16 to turn off.
If, in the above-mentioned state, the lighting switch 12 is manually turned on, the input and ouput terminals Z and Z1 are connected with each other, so current flows to the coil of the relay 8c, so its normally closed contacts open. This cuts off the supply of electric current to the coil of the relay 8b, to turn off causing the headlamps 14a and 14b to turn off.
This known automatic lighting system is not satisfactory in that the lamps 14a, 14b, and 16 inadverdently turn on or off when the system is rendered operable in an automatic lighting mode.
Thus, an object of the present invention is to provide an automatic lighting system which is free from the above-mentioned problem.
A specific object of the present invention is to provide an automatic lighting system which keeps the lamps "ON" even if the signal carrying system (such as the fuse 20 or connectors) of the ignition switch fails during operation in automatic lighting mode.
A still another object of the present invention is to provide an automatic lighting system which does not cause the lamps to turn on when unnecessary.